The invention pertains to peptide-like and peptidomimetic compounds that advantageously inhibit the enzymatic activity of picornaviral 3C proteases, especially rhinovirus 3C proteases (RVPs), and that retard viral growth in cell culture. The invention also relates to the use of such compounds in pharmaceutical compositions and therapeutic treatments for rhinoviral infections. The invention further relates to processes for synthesizing such compounds and compounds useful in such syntheses.
The picornaviruses are a family of tiny non-enveloped positive-stranded RNA-containing viruses that infect humans and other animals. These viruses include the human rhinoviruses, human polioviruses, human coxsackieviruses, human echoviruses, human and bovine enteroviruses, encephalomyocarditis viruses, meningitis virus, foot and mouth viruses, hepatitis A virus, and others. The human rhinoviruses are a major cause of the common cold. To date, there are no effective therapies on the market that cure the common cold, only treatments that relieve the symptoms.
Picornaviral infections may be treated by inhibiting the proteolytic 3C enzymes. These enzymes are required for the natural maturation of the picornaviruses. They are responsible for the autocatalytic cleavage of the genomic, large polyprotein into the essential viral proteins. Members of the 3C protease family are cysteine proteases, where the sulfhydryl group most often cleaves the glutamine-glycine amide bond. Inhibition of 3C proteases is believed to block proteolytic cleavage of the polyprotein, which in turn can retard the maturation and replication of the viruses by interfering with viral particle production. Therefore, inhibiting the processing of this cysteine protease with selective small molecules that are specifically recognized should represent an important and useful approach to treat and cure viral infections of this nature and, in particular, the common cold.
Some small-molecule inhibitors of the enzymatic activity of picornaviral 3C proteases (i.e., antipicornaviral compounds) have been recently discovered. See, for example: U.S. patent application Ser. No. 08/850,398, filed May 2, 1997, now U.S. Pat. No. 5,856,530 by Webber et al.; U.S. patent application Ser. No. 08/991,282, filed Dec. 16, 1997, U.S. Pat. No. 6,020,371 by Dragovich et al.; and U.S. patent application Ser. No. 08/991,739, filed Dec. 16, 1997, U.S. Pat. No. 5,962,487 by Webber et al. These U.S. patent applications, the disclosures of which are incorporated herein by reference, describe certain antipicornaviral compounds. There is still a desire to discover small-molecule compounds that are especially potent antipicornaviral agents.
Thus, an object of this invention is to discover small-molecule compounds that are especially potent antipicornaviral agents. A further object of the invention is to provide intermediates useful for the synthesis of said protease-inhibiting compounds and synthetic methods useful for such syntheses. A yet further object of the invention is to achieve pharmaceutical compositions that are highly effective for treating maladies mediated by inhibition of picornaviral 3C proteases, such as the common cold.
Such objects have been attained through the discovery of compounds of the invention, which are picornaviral 3C protease inhibitors displaying particularly strong antiviral activity. It has surprisingly been discovered that peptido and peptidomimetic compounds containing a five-membered heterocyclic group have high rhinoviral-protease-inhibiting activity. It has further been surprisingly found that the rhinoviral-protease-inhibiting activity of peptido and peptidomimetic compounds may be significantly enhanced by replacing a glutamine-like moiety found in some known rhinoviral-protease-inhibiting compounds with a side-chain comprising a gamma- or delta-lactam.
The inhibitors of the present invention are of the following general formula (I): 
wherein:
Y is xe2x80x94N(Ry)xe2x80x94, xe2x80x94C(Ry)(Ry)xe2x80x94, or xe2x80x94Oxe2x80x94, where each Ry is independently xe2x80x94H or lower alkyl;
R1 is xe2x80x94H, xe2x80x94F, -alkyl, xe2x80x94OH, xe2x80x94SH, or an O-alkyl group;
R2 and R3 are each independently H; 
xe2x80x83or 
xe2x80x83where n is an integer from 0 to 5, A1 is CH or N, A2 and each A3 are independently selected from C(R41)(R41), NR41), S, S(O), S(O)2, and O, and A4 is NH or NR41, where each R41 is independently H or lower alkyl, provided that no more than two heteroatoms occur consecutively in the above-depicted ring formed by A1, A2, (A3)n, A4 and Cxe2x95x90O, and at least one of R2 and R3 is 
R5 and R6 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group;
R7 and R8 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18, xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18, where R17, R18, and R19 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, or an acyl group, provided that at least one of R7 and R8 is an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18, xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18;
R9 is a suitable organic moiety; and
Z and Z1 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94C(O)R21, xe2x80x94CO2R21, xe2x80x94CN, xe2x80x94C(O)NR21R22, xe2x80x94C(O)NR21OR22, xe2x80x94C(S)R21, xe2x80x94C(S)NR21R22, xe2x80x94NO2, xe2x80x94SOR21, xe2x80x94SO2R21, xe2x80x94SO2NR21R22, xe2x80x94SO(NR21)(OR22), xe2x80x94SONR21, xe2x80x94SO3R21, xe2x80x94PO(OR21)2, xe2x80x94PO(R21)(R22), xe2x80x94PO(NR21R22)(OR23), xe2x80x94PO(NR21R22)(NR23R24), xe2x80x94C(O)NR21NR22R23, or xe2x80x94C(S)NR21NR22R23, where R21, R22, R23, and R24 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, an acyl group, or a thioacyl group, or where any two of R21, R22, R23, and R24, together with the atom(s) to which they are bonded, form a heterocycloalkyl group, provided that Z and Z1 are not both H;
or Z1 and R1, together with the atoms to which they are bonded, form a cycloalkyl or heterocycloalkyl group, where Z1 and R1 are as defined above except for moieties that cannot form the cycloalkyl or heterocycloalkyl group;
or Z and Z1, together with the atoms to which they are bonded, form a cycloalkyl or heterocycloalkyl group, where Z and Z1 are as defined above except for moieties that cannot form the cycloalkyl or heterocycloalkyl group.
The invention also pertains to prodrugs, pharmaceutically acceptable salts, pharmaceutically active metabolites, and pharmaceutically acceptable solvates of compounds of the formula I.
In preferred embodiments of the compounds of the formula I, R2 and R3 are each independently H; 
where n is an integer from 0 to 5, each R41 is independently H or lower alkyl, and the stereochemistry at the carbon denoted with an asterisk may be R or S; provided that at least one of R2 and R3 is 
Preferably, R9 is a five-membered heterocycle having one to three heteroatoms selected from O, N, and S. Alternatively, R9 is 
where R2 is 
In other preferred embodiments, the variables of formula I are as follows. Z and Z1 are each independently selected from H, F, lower alkyl, xe2x80x94CO2R21, and xe2x80x94C(O)NR21R22, provided that Z and Z1 are not both H, where R21 and R22 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, an acyl group, or a thioacyl group, or R21 and R22, together with the atom(s) to which they are bonded, form a heterocycloalkyl group. At least one of R2 or R3 is 
and the other is H. R5 and R6 are each independently selected from H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, and a heteroaryl group, more preferably one of R5 and R6 is H and the other is alkyl or aryl (e.g., unsubstituted or substituted phenylmethyl). R7 and R8 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group; and more preferably one of R7 and R8 is H and the other is alkyl (e.g., 2-propyl, 2-methyl-2-propyl, or 2-methyl-1-propyl) or arylmethyl (e.g., unsubstituted or substituted phenylmethyl or naphthylmethyl). R9 is a five-membered heterocycle having from one to three heteroatoms selected from O, N, and S, more preferably a five-membered heterocycle having at least one nitrogen heteroatom and at least one oxygen heteroatom (e.g., unsubstituted or substituted 1,2-oxazolyl (i.e., isoxazolyl), 1,3-oxazolyl (i.e., oxazolyl), or oxadiazolyl (1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, or 1,2,5-oxadiazolyl). When R9 is oxadiazolyl, unsubstituted and monomethyl-substituted 1,2,4-oxadiazolyl are preferred. In especially preferred embodiments, R9 is 3-isoxazolyl or 5-isoxazolyl, either unsubstituted or substituted with one or two methyl groups and/or halogens, with chlorine and fluorine being preferred halogen substituents.
In a preferred embodiment, the compounds, prodrugs, pharmaceutically acceptable salts, pharmaceutically active metabolites, and solvates have an antipicornaviral activity with an EC50 less than or equal to 100 xcexcM in the H1-HeLa cell culture assay, and more preferably an antirhinoviral activity with an EC50 less than or equal to 10 xcexcM in the H1-HeLa cell culture.
In another aspect, the invention is directed to intermediates of formula II, preferably of the formula IIxe2x80x2, which are useful in the synthesis of certain compounds: 
wherein:
p is an integer of from 0 to 5;
A11 is CH or N, A12 and each A13 are independently selected from C(R61)(R61), N(R61), S, S(O), S(O)2, and O, and A14 is NH or NR61, where each R61 is independently H, alkyl, acyl, or aryl, provided that no more than two heteroatoms occur consecutively in the above-depicted ring in formula II formed by A11, A12, (A13)n, A14 and Cxe2x95x90O;
each R141 is independently H or lower alkyl;
R5, is H, alkyl, acyl, or aryl;
R52, R53, and R54 are each independently selected from H, hydroxyl, alkyl, acyl, and aryl; or any two of R52, R53, and R54 together form xe2x95x90O or xe2x95x90C(R57)(R58), where R57 and R58 are each independently selected from H, alkyl, CO2(C1-C6)alkyl, C(O)N(C1-C6)alkyl, and CO2(aryl); and
R55 and R56 are each independently H or a suitable protecting group for nitrogen.
The invention is also directed to pharmaceutically acceptable salts of the compounds of formulae II and IIxe2x80x2.
The invention also relates to pharmaceutical compositions containing a therapeutically effective amount of at least one compound of the formula I, or a prodrug, pharmaceutically acceptable salt, pharmaceutically active metabolite, or solvate thereof. Additionally, the invention relates to methods of inhibiting picornaviral 3C protease by administering a therapeutically effective amount of at least one compound of the formula I, or a prodrug, pharmaceutically acceptable salt, pharmaceutically active metabolite, or solvate thereof.
The present invention relates to compounds of the formula I: 
wherein Y, R1, R2, R3, R5, R6, R7, R8, R9, Z, and Z1 are as defined above, and to pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates thereof. Preferably, such compounds, pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates have antipicornaviral activity, more preferably antirhinoviral activity, corresponding to an EC50 less than or equal to 100 xcexcM in the H1-HeLa cell culture assay, more preferably corresponding to an EC50 less than or equal to 10 xcexcM in the H1-HeLa cell culture assay.
The present invention additionally relates to preferred compounds of the formulas I-A, I-B, and I-C: 
wherein Ry (in formula I-A) is H or lower alkyl, and R1, R2, R3, R5, R6, R7, R8, R9, Z, and Z1 are as defined above, and to pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates thereof.
The inventive compounds of formulas I-A, which are referred to herein as xe2x80x9cpeptide-likexe2x80x9d compounds, I-B, which are referred to herein as xe2x80x9cketomethylene-typexe2x80x9d compounds, and I-C, which are referred to herein as xe2x80x9cdepsipeptidexe2x80x9d compounds, differ in their backbones, which may affect the specific biodistribution or other physical properties; nonetheless each possesses a strong rhinoviral-protease-inhibiting activity.
In preferred embodiments of compounds of formulas I-A, I-B, and I-C above:
R1 is H, F, or an alkyl group;
Ry (in formula I-A) is H or methyl;
R3, R5, and R8 are each H;
R2 is selected from one of the following moieties: 
R6 is an alkyl group, which has as a preferred optional substituent an aryl group;
R7 is an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group;
R9 is a five-membered heterocycle having from one to three heteroatoms selected from O, N, and S, preferably where at least one of the heteroatoms is nitrogen, that is unsubstituted or substituted, where the optional substituents are preferably halogen or lower alkyl, and more preferably mono-chloro or -fluoro or a methyl group; and
Z and Z1 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94C(O)R21, xe2x80x94CO2R21, xe2x80x94CN, xe2x80x94C(O)NR21R22, xe2x80x94C(O)NR21OR22, xe2x80x94C(S)R21, xe2x80x94C(S)NR21R22, xe2x80x94NO2, xe2x80x94SOR21, xe2x80x94SO2R21, xe2x80x94SO2NR21R22, xe2x80x94SO(NR21)(OR22), xe2x80x94SONR21, xe2x80x94SO3R21, xe2x80x94PO(OR21)2, xe2x80x94PO(R21)(R22), xe2x80x94PO(NR21R22)(OR23), xe2x80x94PO(NR21R22)(NR23R24), xe2x80x94C(O)NR21NR22R23, or xe2x80x94C(S)NR21NR22R23, where Z and Z1 are not both H, and where R21, R22, R23, and R24 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, an acyl group, or a thioacyl group, or where any two of R21, R22, R23, and R24, together with the atom(s) to which they are bonded, form a heterocycloalkyl group,
or Z and Z1 (both as defined above), together with the atoms to which they are attached, form a heterocycloalkyl group.
In preferred embodiments, the compounds of the invention are of the formulae I-Axe2x80x2, I-Bxe2x80x2, and I-Cxe2x80x2: 
wherein:
R1, Z, and Z1 are as defined above;
n is 1 or 2;
Ry (in formula I-Axe2x80x2) is H or lower alkyl;
R6 is alkyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl;
R7 is alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18, xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18, where R17, R18, and R19 are each independently H, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, or acyl;
R9 is a five-membered heterocycle having one to three heteroatoms selected from O, N, and S, that is unsubstituted or substituted, where the optional substituents are preferably one or two lower alkyl groups and/or halogens; and
R20 is H.
The invention also relates to prodrugs, pharmaceutically acceptable salts, pharmaceutically active metabolites, and solvate of such compounds.
In preferred embodiments, the RVP-inhibiting agents of the invention are compounds of any of the stereospecific formulas I-Axe2x80x3, I-Bxe2x80x3, and I-Cxe2x80x3: 
wherein Ry, R1, R2, R6, R7, R9, Z, and Z1 are as defined above, and pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates thereof.
In preferred embodiments of compounds of the formula I-Axe2x80x3, I-Bxe2x80x3, or I-Cxe2x80x3:
R1 is H, F, or methyl;
Ry (in formula I-Axe2x80x2) is H or methyl;
R2 is selected from one of the following moieties: 
R6 is arylmethyl or arylthiomethyl, where aryl is preferably an optionally substituted phenyl group;
R7 is an alkyl group, more preferably selected from 2-propyl, 2-methyl-2-propyl, 2-methyl-1-propyl, and arylmethyl, where the aryl group is preferably phenyl or naphthyl;
R9 is isoxazolyl, oxazolyl, or oxadiazolyl, optionally substituted with one or two lower alkyl groups and/or halogens; and
Z is H, and Z1 is xe2x80x94CO2R21, xe2x80x94CN, or xe2x80x94C(O)NR21R22, where R21 and R22 are as defined above, or Z and Z1 together form a cyclic ester or amide.
Even more preferably, the RVP-inhibiting agents of the invention are compounds of any of the formulas I-Axe2x80x2xe2x80x3, I-Bxe2x80x2xe2x80x3, and I-Cxe2x80x2xe2x80x3: 
wherein n, Ry, R1, R20, R6, R7, R9, Z, and Z1 are as defined above, and pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates thereof.
In preferred compounds of the formula (I-Axe2x80x2xe2x80x3), (I-Bxe2x80x2xe2x80x3), or (I-Cxe2x80x2xe2x80x3):
R1 is H, F, or methyl;
Ry (in formula I-Axe2x80x2) is H or methyl;
R20 is hydrogen;
R6 is arylmethyl or arylthiomethyl, where aryl is preferably phenyl unsubstituted or substituted with halogen, lower alkyl, and/or lower alkoxy;
R7 is an alkyl group, and more preferably is selected from 2-propyl, 2-methyl-2-propyl, 2-methyl-1-propyl, and arylmethyl, where the aryl group is preferably phenyl or naphthyl;
R9 is isoxazolyl, oxazolyl, or oxadiazolyl, each optionally substituted with one or two lower alkyl groups and/or halogens; and
Z is H, and Z1 is xe2x80x94CO2R21, xe2x80x94CN, or xe2x80x94C(O)NR21R22, where R21 and R22 are as defined above, or Z and Z1 together form a cyclic ester or amide.
In especially preferred compounds of the invention of the generic formula I (and subgeneric formulae), R1 is H or F.
In another aspect, the invention is directed to intermediate compounds of the formulas II and IIxe2x80x2: 
wherein the variables (p, A11, A12, A13, A14, R51, R52, R53, R54, R55, R56, and R141) are as defined above. These compounds are useful for synthesizing pharmaceutically useful compounds of the formula I.
Preferred R55 and R56 groups are H and suitable protecting groups for nitrogen, for example, BOC (t-butyloxycarbonyl), CBZ (benzyloxycarbonyl), FMOC (fluorene-9-methyloxycarbonyl), other alkyloxycarbonyls (e.g. methyloxycarbonyl), and trityl (triphenylmethyl). Other suitable nitrogen-protecting groups may be readily selected by artisans (see, e.g., Greene and Wutz, Protecting Groups in Chemical Synthesis (2nd ed.), John Wiley and Sons, NY (1991)). Preferred groups for R52, R53, and R54 are H, alkoxy, hydroxy, and carbonyl.
Preferred formula-II compounds include the following, where PN is a suitable protecting group for nitrogen and q is 1 or 2: 
Other preferred intermediates include the following compounds, where BOC is t-butyloxycarbonyl: 
Of these, the preferred stereoisomers are: 
Especially preferred intermediates include the following compounds: 
In accordance with a convention used in the art, 
is used in structural formulas herein to depict the bond that is the point of attachment of the moiety or substituent to the core or backbone structure.
Where chiral carbons are included in chemical structures, unless a particular orientation is depicted, both stereoisomeric forms are intended to be encompassed.
As used herein, the term xe2x80x9calkyl groupxe2x80x9d is intended to mean a straight- or branched-chain monovalent radical of saturated and/or unsaturated carbon atoms and hydrogen atoms, such as methyl (Me), ethyl (Et), propyl, isopropyl, butyl, isobutyl, t-butyl, ethenyl, pentenyl, butenyl, propenyl, ethynyl, butynyl, propynyl, pentynyl, hexynyl, and the like, which may be unsubstituted (i.e., containing only carbon and hydrogen) or substituted by one or more suitable substituents as defined below (e.g., one or more halogens, such as F, Cl, Br, or I, with F and Cl being preferred). A xe2x80x9clower alkyl groupxe2x80x9d is intended to mean an alkyl group having from 1 to 4 carbon atoms in its chain.
A xe2x80x9ccycloalkyl groupxe2x80x9d is intended to mean a non-aromatic monovalent monocyclic, bicyclic, or tricyclic radical containing 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 carbon ring atoms, each of which may be saturated or unsaturated, and which may be unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more heterocycloalkyl groups, aryl groups, or heteroaryl groups, which themselves may be unsubstituted or substituted by one or more substituents. Illustrative examples of cycloalkyl groups include the following moieties: 
A xe2x80x9cheterocycloalkyl groupxe2x80x9d is intended to mean a non-aromatic monovalent monocyclic, bicyclic, or tricyclic radical, which is saturated or unsaturated, containing 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 ring atoms, which includes 1, 2, 3, 4, or 5 heteroatoms selected from nitrogen, oxygen, and sulfur, where the radical is unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more cycloalkyl groups, aryl groups, or heteroaryl groups, which themselves may be unsubstituted or substituted by one or more suitable substituents. Illustrative examples of heterocycloalkyl groups include the following moieties: 
An xe2x80x9caryl groupxe2x80x9d is intended to mean an aromatic monovalent monocyclic, bicyclic, or tricyclic radical containing 6, 10, 14, or 18 carbon ring atoms, which may be unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more cycloalkyl groups, heterocycloalkyl groups, or heteroaryl groups, which themselves may be unsubstituted or substituted by one or more suitable substituents. Illustrative examples of aryl groups include the following moieties: 
A xe2x80x9cheteroaryl groupxe2x80x9d is intended to mean an aromatic monovalent monocyclic, bicyclic, or tricyclic radical containing 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 ring atoms, including 1, 2, 3, 4, or 5 heteroatoms selected from nitrogen, oxygen, and sulfur, which may be unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more cycloalkyl groups, heterocycloalkyl groups, or aryl groups, which themselves may be unsubstituted or substituted by one or more suitable substituents. Illustrative examples of heteroaryl groups include the following moieties: 
A xe2x80x9cheterocyclexe2x80x9d is intended to mean a heteroaryl or heterocycloalkyl group (each of which, as defined above, are optionally substituted).
An xe2x80x9cacyl groupxe2x80x9d is intended to mean a xe2x80x94C(O)xe2x80x94R radical, where R is a substituent as defined below.
A xe2x80x9cthioacyl groupxe2x80x9d is intended to mean a xe2x80x94C(S)xe2x80x94R radical, where R is a substituent as defined below.
A xe2x80x9csulfonyl groupxe2x80x9d is intended to mean a xe2x80x94SO2R radical, where R is a substituent as defined below.
A xe2x80x9chydroxy groupxe2x80x9d is intended to mean the radical xe2x80x94OH.
An xe2x80x9camino groupxe2x80x9d is intended to mean the radical xe2x80x94NH2.
An xe2x80x9calkylamino groupxe2x80x9d is intended to mean the radical xe2x80x94NHRa, where Ra is an alkyl group.
A xe2x80x9cdialkylamino groupxe2x80x9d is intended to mean the radical xe2x80x94NRaRb, where Ra and Rb are each independently an alkyl group.
An xe2x80x9calkoxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORa, where Ra is an alkyl group. Exemplary alkoxy groups include methoxy, ethoxy, propoxy, and the like.
An xe2x80x9calkoxycarbonyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)ORa, where Ra is an alkyl group.
An xe2x80x9calkylsulfonyl groupxe2x80x9d is intended to mean the radical xe2x80x94SO2Ra, where Ra is an alkyl group.
An xe2x80x9calkylaminocarbonyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)NHRa, where Ra is an alkyl group.
A xe2x80x9cdialkylaminocarbonyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)NRaRb, where Ra and Rb are each independently an alkyl group.
A xe2x80x9cmercapto groupxe2x80x9d is intended to mean the radical xe2x80x94SH.
An xe2x80x9calkylthio groupxe2x80x9d is intended to mean the radical xe2x80x94SRa, where Ra is an alkyl group.
A xe2x80x9ccarboxy groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)OH.
A xe2x80x9ccarbamoyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)NH2.
An xe2x80x9caryloxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORc, where Rc is an aryl group.
A xe2x80x9cheteroaryloxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORd, where Rd is a heteroaryl group.
An xe2x80x9carylthio groupxe2x80x9d is intended to mean the radical xe2x80x94SRc, where Rc is an aryl group.
A xe2x80x9cheteroarylthio groupxe2x80x9d is intended to mean the radical xe2x80x94SRd, where Rd is a heteroaryl group.
The term xe2x80x9csuitable organic moietyxe2x80x9d is intended to mean any organic moiety recognizable, such as by routine testing, to those skilled in the art as not adversely affecting the inhibitory activity of the inventive compounds. Illustrative examples of suitable organic moieties include, but are not limited to, hydroxy groups, alkyl groups, oxo groups, cycloalkyl groups, heterocycloalkyl groups, aryl groups, heteroaryl groups, acyl groups, sulfonyl groups, mercapto groups, alkylthio groups, alkoxy groups, carboxy groups, amino groups, alkylamino groups, dialkylamino groups, carbamoyl groups, arylthio groups, heteroarylthio groups, and the like.
The term xe2x80x9csubstituentxe2x80x9d or xe2x80x9csuitable substituentxe2x80x9d is intended to mean any suitable substituent that may be recognized or selected, such as through routine testing, by those skilled in the art. Illustrative examples of suitable substituents include hydroxy groups, halogens, oxo groups, alkyl groups, acyl groups, sulfonyl groups, mercapto groups, alkylthio groups, alkoxy groups, cycloalkyl groups, heterocycloalkyl groups, aryl groups, heteroaryl groups, carboxy groups, amino groups, alkylamino groups, dialkylamino groups, carbamoyl groups, aryloxy groups, heteroaryloxy groups, arylthio groups, heteroarylthio groups, and the like.
The term xe2x80x9coptionally substitutedxe2x80x9d is intended to expressly indicate that the specified group is unsubstituted or substituted by one or more suitable substituents, unless the optional substituents are expressly specified, in which case the term indicates that the group is unsubstituted or substituted with the specified substituents. As defined above, various groups may be unsubstituted or substituted (i.e., they are optionally substituted) unless indicated otherwise herein (e.g., by indicating that the specified group is unsubstituted).
A xe2x80x9cprodrugxe2x80x9d is intended to mean a compound that is converted under physiological conditions or by solvolysis or metabolically to a specified compound that is pharmaceutically active.
A xe2x80x9cpharmaceutically active metabolitexe2x80x9d is intended to mean a pharmacologically active product produced through metabolism in the body of a specified compound.
A xe2x80x9csolvatexe2x80x9d is intended to mean a pharmaceutically acceptable solvate form of a specified compound that retains the biological effectiveness of such compound. Examples of solvates include compounds of the invention in combination with water, isopropanol, ethanol, methanol, DMSO, ethyl acetate, acetic acid, or ethanolamine.
A xe2x80x9cpharmaceutically acceptable saltxe2x80x9d is intended to mean a salt that retains the biological effectiveness of the free acids and bases of the specified compound and that is not biologically or otherwise undesirable. Examples of pharmaceutically acceptable salts include sulfates, pyrosulfates, bisulfates, sulfites, bisulfites, phosphates, monohydrogenphosphates, dihydrogenphosphates, metaphosphates, pyrophosphates, chlorides, bromides, iodides, acetates, propionates, decanoates, caprylates, acrylates, formates, isobutyrates, caproates, heptanoates, propiolates, oxalates, malonates, succinates, suberates, sebacates, fumarates, maleates, butyne-1,4-dioates, hexyne-1,6-dioates, benzoates, chlorobenzoates, methylbenzoates, dinitrobenzoates, hydroxybenzoates, methoxybenzoates, phthalates, sulfonates, xylenesulfonates, phenylacetates, phenylpropionates, phenylbutyrates, citrates, lactates, xcex3-hydroxybutyrates, glycollates, tartrates, methane-sulfonates, propanesulfonates, naphthalene-1-sulfonates, naphthalene-2-sulfonates, and mandelates.
If an inventive compound is a base, a desired salt may be prepared by any suitable method known to the art, including treatment of the free base with an inorganic acid, such as hydrochloric acid; hydrobromic acid; sulfuric acid; nitric acid; phosphoric acid; and the like, or with an organic acid, such as acetic acid; maleic acid; succinic acid; mandelic acid; fumaric acid; malonic acid; pyruvic acid; oxalic acid; glycolic acid; salicylic acid; pyranosidyl acid, such as glucuronic acid or galacturonic acid; alpha-hydroxy acid, such as citric acid or tartaric acid; amino acid, such as aspartic acid or glutamic acid; aromatic acid, such as benzoic acid or cinnamic acid; sulfonic acid, such as p-toluenesulfonic acid or ethanesulfonic acid; or the like.
If an inventive compound is an acid, a desired salt may be prepared by any suitable method known to the art, including treatment of the free acid with an inorganic or organic base, such as an amine (primary, secondary, or tertiary); an alkali metal or alkaline earth metal hydroxide; or the like. Illustrative examples of suitable salts include organic salts derived from amino acids such as glycine and arginine; ammonia; primary, secondary, and tertiary amines; and cyclic amines, such as piperidine, morpholine, and piperazine; as well as inorganic salts derived from sodium, calcium, potassium, magnesium, manganese, iron, copper, zinc, aluminum, and lithium.
In the case of compounds, salts, or solvates that are solids, it is understood by those skilled in the art that the inventive compounds, salts, and solvates may exist in different crystal forms, all of which are intended to be within the scope of the present invention and specified formulas.
The inventive compounds may exist as single stereoisomers, racemates, and/or mixtures of enantiomers and/or diastereomers. All such single stereoisomers, racemates, and mixtures thereof are intended to be within the broad scope of the present invention. Preferably, however, the inventive compounds are used in optically pure form.
As generally understood by those skilled in the art, an optically pure compound is one that is enantiomerically pure. As used herein, the term xe2x80x9coptically purexe2x80x9d is intended to mean a compound comprising at least a sufficient activity. Preferably, an optically amount of a single enantiomer to yield a compound having the desired pharmacological pure compound of the invention comprises at least 90% of a single isomer (80% enantiomeric excess), more preferably at least 95% (90% e.e.), even more preferably at least 97.5% (95% e.e.), and most preferably at least 99% (98% e.e.).
Preferably in the compounds of the formula I (or of any of the subgeneric formula), R1 is H or F.
In the compounds of formula I, preferably R9 is an unsubstituted or substituted isoxazolyl group, where the optional substituents are preferably one or two methyl groups and/or halogens.
Especially preferred embodiments of the invention are described below in reference to the following formula I-Axe2x80x3: 
Preferred compounds of the present invention include peptido (peptide-like) Compounds (A-1)-(A-8) of the formula I-Axe2x80x3 above, wherein R1 is H, Z is H, Ry is H, and R2, R6, R7, Z1, and R9 are as respectively defined below:
(A-1) R2 is CH2CH2C(O)NH2, R6 is CH2Ph, R7 is CH2CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
(A-2) R2 is CH2CH2C(O)NH2, R6 is CH2Ph, R7 is CH2CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
(A-3) R2 is CH2CH2C(O)NH2, R6 is 
R7 is C(CH3)3, Z1 is CO2CH2CH3, and R9 is 
(A-4) R2 is CH2CH2C(O)NH2, R6 is 
R7 is C(CH3)3, Z1 is CO2CH2CH3, and R9 is 
(A-5) R2 is 
R6 is 
R7 is CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
(A-6) R2 is CH2CH2C(O)NH2, R6 is 
R7 is CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
(A-7) R2 is 
R6 is 
R7 is C(CH3)3, Z1 is CO2CH2CH3, and R9 is 
(A-8) R2 is 
R6 is 
R7 is CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
Preferred peptide-like compounds of the formula I-Axe2x80x3xe2x80x3 further include Compounds (A-9)-(A-13) below, wherein R1 is H, Z is H, Z1 is CO2CH2CH3, Ry is CH3, and R2, R6, R7, and R9 are as respectively defined below:
(A-9) R2 is CH2CH2C(O)NH2, R6 is 
R7 is 
and R9 is 
(A-10) R2 is CH2CH2C(O)NH2, R6 is CH2Ph, R7 is CH2CH(CH3)2, and R9 is 
(A-11) R2 is CH2CH2C(O)NH2, R6 is 
R7 is 
and R9 is 
(A-12) R2 is CH2CH2C(O)NH2, R6 is 
R7 is CH2CH(CH3)2, and R9 is 
(A-13) R2 is CH2CH2C(O)NH2, R6 is 
R7 is 
and R9 is 
Other preferred peptide-like compounds include the following: 
Preferred ketomethylene-type Compounds (B-1)-(B-4) of the invention are described below in reference to the following formula I-Bxe2x80x3: 
(B-1) R2 is CH2CH2C(O)NH2, R6 is 
R7 is CH(CH3)2, Z is H, Z1 is CO2CH2CH3, and R9 is 
(B-2) R2 is 
R6 is 
R7 is CH(CH3)2, Z is H, Z1 is CO2CH2CH3, and R9 is 
(B-3) R2 is 
R6 is 
R7 is CH(CH3)2, Z and Z1 together are 
where the carbonyl group is cis to the hydrogen corresponding to R1 in formula I, and R9 is 
(B-4) R2 is 
R6 is 
R7 is CH(CH3)2, Z is H, Z1 is CO2CH2CH3, and R9 is 
Preferred depsipeptide-type Compounds (C-1) and (C-2) of the invention are described below in reference to the following formula I-Cxe2x80x3, where R1 is H: 
(C-1) Z is H, R2 is CH2CH2C(O)NH2, R6 is 
R7 is CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
(C-2) Z is H, R2 is 
R6 is 
R7 is CH(CH3)2, Z1 is CO2CH2CH3, and R9 is 
Additional compounds may be prepared in reference to formula I by selecting the variables from the following substituents:
Ry=H or CH3;
R1=H or CH3; 
xe2x80x83or phenylmethyl (i.e., benzyl), where the aryl group is optionally substituted with one, two, or three substituents each independently selected from halogens, methoxy and methyl;
R7=2-methyl-1-propyl, 2-propyl, 2-methyl-2-propyl, benzyl, or 
xe2x80x83and 
The present invention is also directed to a method of inhibiting picornaviral 3C protease activity, comprising contacting the protease with an effective amount of a compound of formula I, or a pharmaceutically acceptable salt, prodrug, pharmaceutically active metabolite, or solvate thereof. For example, picornaviral 3C protease activity may be inhibited in mammalian tissue by administering a compound of formula I or a pharmaceutically acceptable salt, prodrug, pharmaceutically active metabolite, or solvate thereof. More preferably, the present method is directed at inhibiting rhinoviral protease activity.
xe2x80x9cTreatingxe2x80x9d or xe2x80x9ctreatmentxe2x80x9d is intended to mean at least the mitigation of a disease condition in a mammal, such as a human, that is alleviated by the inhibition of the activity of one or more picornaviral 3C proteases, such as human rhinoviruses, human poliovirus, human coxsackieviruses, encephalomyocarditis viruses, meningitis virus, and hepatitis A virus, and includes: (a) prophylactic treatment in a mammal, particularly when the mammal is found to be predisposed to having the disease condition but not yet diagnosed as having it; (b) inhibiting the disease condition; and/or (c) alleviating, in whole or in part, the disease condition.
The activity of the inventive compounds as inhibitors of picornaviral 3C protease activity may be measured by any of the suitable methods known to those skilled in the art, including in vivo and in vitro assays. An example of a suitable assay for activity measurements is the antiviral H1-HeLa cell culture assay described herein.
Administration of the compounds of the formula I and their pharmaceutically acceptable prodrugs, salts, active metabolites, and solvates may be performed according to any of the accepted modes of administration available to those skilled in the art. Illustrative examples of suitable modes of administration include oral, nasal, parenteral, topical, transdermal, and rectal. Intranasal delivery is especially preferred.
An inventive compound of formula I or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof may be administered as a pharmaceutical composition in any pharmaceutical form recognizable to the skilled artisan as being suitable. Suitable pharmaceutical forms include solid, semisolid, liquid, or lyophilized formulations, such as tablets, powders, capsules, suppositories, suspensions, liposomes, and aerosols. Pharmaceutical compositions of the invention may also include suitable excipients, diluents, vehicles, and carriers, as well as other pharmaceutically active agents, depending upon the intended use. In preferred embodiments, the inventive pharmaceutical compositions are delivered intranasally in the form of suspensions.
Acceptable methods of preparing suitable pharmaceutical forms of the pharmaceutical compositions are known or may be routinely determined by those skilled in the art. For example, pharmaceutical preparations may be prepared following conventional techniques of the pharmaceutical chemist involving steps such as mixing, granulating, and compressing when necessary for tablet forms, or mixing, filling, and dissolving the ingredients as appropriate, to give the desired products for oral, parenteral, topical, intravaginal, intranasal, intrabronchial, intraocular, intraaural, and/or rectal administration.
Solid or liquid pharmaceutically acceptable carriers, diluents, vehicles, or excipients may be employed in the pharmaceutical compositions. Illustrative solid carriers include starch, lactose, calcium sulfate dihydrate, terra alba, sucrose, talc, gelatin, pectin, acacia, magnesium stearate, and stearic acid. Illustrative liquid carriers include syrup, peanut oil, olive oil, saline solution, and water. The carrier or diluent may include a suitable prolonged-release material, such as glyceryl monostearate or glyceryl distearate, alone or with a wax. When a liquid carrier is used, the preparation may be in the form of a syrup, elixir, emulsion, soft gelatin capsule, sterile injectable liquid (e.g., solution), or a nonaqueous or aqueous liquid suspension.
A dose of the pharmaceutical composition contains at least a therapeutically effective amount of the active compound (i.e., a compound of formula I or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof), and preferably is made up of one or more pharmaceutical dosage units. The selected dose may be administered to a mammal, for example, a human patient, in need of treatment mediated by inhibition of picornaviral 3C protease activity, by any known or suitable method of administering the dose, including topically, for example, as an ointment or cream; orally; rectally, for example, as a suppository; parenterally by injection; or continuously by intravaginal, intranasal, intrabronchial, intraaural, or intraocular infusion.
A xe2x80x9ctherapeutically effective amountxe2x80x9d is intended to mean the amount of an inventive compound that, when administered to a mammal in need thereof, is sufficient to effect treatment for disease conditions alleviated by the inhibition of the activity of one or more picornaviral 3C proteases, such as human rhinoviruses, human poliovirus, human coxsackieviruses, encephalomyocarditis viruses, menigovirus, and hepatitis A virus. The amount of a given compound of the invention that will be therapeutically effective will vary depending upon factors such as the particular compound, the disease condition and the severity thereof, the identity of the mammal in need thereof, which amount may be routinely determined by artisans.
By way of illustration, a formulation for nasal delivery of the inventive compounds for treatment of rhinoviral infections can be prepared as follows, where all percentages are weight/weight and the suspension is prepared in purified water. A formula-I compound is micronized to a reduced particle size such that D90 less than 10 xcexcm. A suspension is prepared to contain a final concentration of from about 0.01% to about 2% of the active compound, preferably about from 0.2% to 2%. An appropriate preservative selected from those known in the art may be included, for example, benzalkonium chloride/EDTA, in appropriate final-concentration ranges, e.g., about 0.02%/0.01%. A suspending agent, such as mixture of microcrystalline cellulose (final concentration of about 1%-1.5%, preferably about 1.2%) and sodium carboxymethylcellulose cellulose (final concentration of about 0.1%-0.2%, preferably about 0.13%) may be included. A surfactant such as polysorbate 80 may be included in a final concentration of about from 0.05% to 0.2%, preferably about 0.1%. A tonicity modifier such as dextrose may be included to give a final concentration of about from 4% to 6%, preferably about 5%. The pH of the final solution is adjusted as appropriate to a physiological range, e.g., 4-6, using non-toxic acid and/or base, such as HCl and/or NaOH.
An exemplary formulation for nasal delivery of the inventive compound of Example 17 has the following composition, where all percentages are weight/weight and the suspension is prepared in purified water:
The inventive compounds of formula (I) may be advantageously prepared by the methods of the present invention, including the general methods described below. In each of these general methods, R1, R2, R3, R5, R6, R7, R8, R9, Ry, Z, and Z1 are as defined above, and R4 is used (as a shorthand representation) to mean: 
where R7, R8, and R9 are as defined above.
In General Method I, useful for synthesis of peptide-like compounds of formula I-A, an amino acid A, where P1 is an appropriate protecting group for nitrogen, is subjected to an amide-forming reaction with amino alcohol (or salt thereof) B to produce amide C. Compound C is then deprotected to give free amine (or salt thereof) D. Amine D and amino acid E, which may incorporate either an R4 group or a protecting group for nitrogen (P2), are subjected to a bond-forming reaction generating compound F. Compound F is oxidized to intermediate G, which is then transformed into unsaturated product H. If protecting groups have been used on amino acid E, or on any R groups (R1-R9) and/or on Ry and/or on Z and/or Z1, product H is deprotected and/or further modified to yield deprotected or modified H. 
An alternative method to prepare intermediate F is described as follows. Amino acid E and amino acid (or salt thereof) I, where P3 is an appropriate protecting group for oxygen, are subjected to a bond-forming reaction to produce intermediate J. Molecule J is deprotected to yield free carboxylic acid K, which is subsequently subjected to an amide-forming reaction with amino alcohol (or salt thereof) B to generate intermediate F. 
In General Method II, which is also useful for synthesizing peptide-like compounds of formula I-A, an amino acid L, where P1 is an appropriate protecting group for nitrogen, is converted to a carbonyl derivative M, where xe2x80x9cLvxe2x80x9d is a leaving group. Compound M is subjected to a reaction where Lv is replaced by R1 to give derivative N. Derivative N is then transformed into unsaturated product O. Unsaturated compound O is deprotected to give free amine (or salt thereof) P, or modified at Z or Z1 first to give Oxe2x80x2, and then deprotected to P. Intermediate P is subsequently subjected to an amide-forming reaction with carboxylic acid K to give final product H. If protecting groups have been used on any R group (R1-R9) and/or on Ry and/or on Z and/or Z1, product H is deprotected and/or further modified to yield deprotected or modified H. 
An alternative method to prepare intermediate N is described as follows. Compound M is subjected to a reaction where xe2x80x9cLvxe2x80x9d (or more particularly xe2x80x94C(O)xe2x80x94Lv), is reduced to protected amino alcohol Q. Intermediate Q is subsequently oxidized to derivative N. 
In General Method III, useful for synthesis of peptide-like compounds of formula I-A, an amino acid L, where P1 is an appropriate protecting group for nitrogen, is converted to a carbonyl derivative M, where xe2x80x9cLvxe2x80x9d is a leaving group. Compound M is deprotected to give free amine (or salt thereof) R, which subsequently is subjected to an amide-forming reaction with carboxylic acid K to give intermediate S. Compound S is then either directly converted to carbonyl intermediate G, or successively reduced to alcohol F first, which is oxidized to G. Compound G is subjected to a reaction to yield the unsaturated final product H. If protecting groups have been used on any R groups (R1-R9) and/or on Ry and/or on Z and/or Z1, product H is deprotected and/or further modified to yield deprotected or modified H. 
In General Method IV, useful for synthesis of peptide-like compounds of formula I-A, free amine (or salt thereof) P, prepared from intermediate O as described in General Method II, is converted to amide T by reaction with amino acid A, where P1 is an appropriate protecting group for nitrogen. Compound T is further deprotected to free amine (or salt thereof) U, which is subsequently converted to H with amino acid E. If protecting groups have been used on any R groups (R1-R9) and/or on Ry and/or on Z and/or Z1, product H is deprotected and/or further modified to yield deprotected or modified H. 
In General Method V, useful for synthesis of ketomethylene compounds of formula I-B, optically active lactone AA, where P4 is an appropriate protecting group for nitrogen, and R5 and R8 are H (which may be prepared by the method described below and by various literature methods, including: (a) Herold et al., J. Org. Chem. 1989, 54, 1178; (b) Bradbury et al., Tetrahedron Lett. 1989, 30, 3845; (c) Bradbury et al., J. Med. Chem. 1990, 33, 2335; (d) Wuts et al., J. Org. Chem. 1992, 57, 6696; (e) Jones et al., J. Org. Chem. 1993, 58, 2286; (f) Pxc3xa9gorier et al., Tetrahedron Lett. 1995, 36, 2753; and (g) Dondoni et al., J. Org. Chem. 1995, 60, 7927) is transformed by a two-step procedure (basic hydrolysis and subsequent oxidation) into carboxylic acid BB. This material is not isolated, but is subjected to an amide-forming reaction with amine (or salt thereof) P to provide final product CC. The P4 protecting group, along with any additional protecting groups that have been used on any R groups (R1, R2, R3, R6, and/or R7) and/or on Z and/or on Z1, is subsequently deprotected and/or further modified to yield deprotected or modified CC. 
Lactone AA may be prepared in optically active form by the following General Method VI (see: Herold et al., J. Org. Chem. 1989, 54, 1178; Bradbury et al., Tetrahedron Lett. 1989, 30, 3845; and Bradbury et al., J. Med. Chem. 1990, 33, 2335). A xcex3,xcex4-unsaturated carboxylic acid DD, which incorporates R7, is transformed into the corresponding acid chloride (not shown). This acid chloride is subjected to an amide-forming reaction with a chiral amine or a chiral oxazolidone to provide derivative EE (in which X1 is a chiral amine or a chiral oxazolidone). Compound EE is subsequently deprotonated, and the resulting enolate is diastereoselectively alkylated with an electrophile corresponding to R6 to provide compound FF, where R5 is H. This material is then subjected to a halolactonization reaction to provide halo-lactone GG, in which R5 and R8 are H and xe2x80x9chalxe2x80x9d is Br or I. Halo-lactone GG is subsequently transformed into azide HH, and this material is then converted into lactone AA, where P4 is an appropriate protecting group for nitrogen. 
xcex3,xcex4-Unsaturated carboxylic acid DD may be prepared by the following General Method VII (see: Herold et al., J. Org. Chem. 1989, 54, 1178). An aldehyde II, which incorporates R7, is coupled with vinylmagnesium bromide to give alcohol JJ. Alcohol JJ is then transformed into xcex3,xcex4-unsaturated carboxylic acid DD by a three-step procedure as follows: (i) treatment with diethyl malonate and catalytic Ti(OEt)4 at 160xc2x0 C. for 1 hour, (ii) heating at 190xc2x0 C. for 4 hours, and (iii) hydrolysis with ethanolic KOH at reflux. 
Carboxylic acid BB may also be prepared by General Method VIII (see Hoffman et al., Tetrahedron, 1997, 53, 7119). An amino acid KK, which incorporates R7 and where P4 is an appropriate protecting group for nitrogen, is transformed into xcex2-ketoester LL. Compound LL is deprotonated and the resulting anion is condensed with triflate MM, which incorporates R6. The coupling product thus obtained is treated with trifluoroacetic acid to provide ketoester NN, and this material is subsequently hydrolyzed to afford carboxylic acid BB. If basic hydrolysis results in epimerization, ketoester NN can be transesterified (allyl alcohol, Ti(Oi-Pr)4) and subsequently deprotected under neutral conditions (Pd(PPh3)4, morpholine) to give carboxylic acid BB. Triflate MM, in turn, may be prepared from the corresponding alcohol by treatment with trifluoromethanesulfonic anhydride and 2,6-lutidine. 
Lactone AA may also be prepared by General Method IX (see: Askin et al., J. Org. Chem. 1992, 57, 2771; and McWilliams et al., J. Am. Chem. Soc. 1996, 118, 11970). An amino acid KK, which incorporates R7 and where P4 is an appropriate protecting group for nitrogen, is transformed into epoxide OO (single diastereomer) by the method described in Luly et al., J. Org. Chem. 1987, 52, 1487. Epoxide OO is condensed with the anion derived from compound PP, which incorporates R6 and in which X2 is a chiral auxiliary (including (1S,2R)-1-aminoindan-2-ol acetonide) to afford coupling product QQ. This material is subsequently cyclized under acidic conditions to provide lactone AA. Compound PP may be prepared from the corresponding carboxylic acid (not shown) by the method outlined in Askin et al., J. Org. Chem. 1992, 57, 2771. 
General Method X, useful in preparation of depsipeptide compounds of the formula I-C, illustrates a method to prepare intermediate TT. Amino acid E and alcohol RR, where P5 is an appropriate protecting group for oxygen, are subjected to an ester bond-forming reaction to produce intermediate SS. Molecule SS is deprotected to yield free carboxylic acid TT, which may be utilized in lieu of carboxylic acid K in any of the general methods described above. 
The following specific methods may also be used to prepare various compounds according to the invention.
Specific Method I describes the preparation of specific intermediate O1, which may be utilized as intermediate O in the general methods described above. Thus, ester A1 (prepared as described in Chida et al., J. Chem. Soc., Chem. Commun. 1992, 1064) is hydrolyzed to give acid B1, which, in turn, is transformed into oxazolidinone C1. Compound C1 is subsequently deprotonated, and the resulting enolate is diastereoselectively alkylated to give allyl intermediate D1. This entity is oxidized via ozonolysis, and the resulting aldehyde (not shown) is subjected to a reductive amination reaction producing lactam E1. Acid-catalyzed methanolysis of E1 then affords alcohol F1. This intermediate is oxidized via the method of Swern (or other suitable oxidation conditions) to the resulting aldehyde (not shown), which is subsequently subjected to an olefin-forming reaction to provide specific intermediate O1. 
Specific Method II describes the preparation of specific intermediate O2, which may be utilized as intermediate O in the general methods described above. Allyl intermediate D1 is subjected to a hydroboration/oxidation sequence to afford a primary alcohol (not shown). This entity is oxidized via the method of Swern (or other suitable oxidation conditions), and the resulting aldehyde (not shown) is subjected to a reductive-amination reaction, producing lactam G1. Acid-catalyzed methanolysis of G1 then affords alcohol H1. This intermediate is oxidized via the method of Swern (or other suitable oxidation conditions) to the resulting aldehyde (not shown), which is subsequently subjected to an olefin-forming reaction to provide specific intermediate O2. 
The following intermediates P1, P2, and P3 may be used in the above general methods in place of intermediate O, to vary the substituent group in the R2position. 
A synthesis of intermediate P1 is described below. Intermediate C1 (described above) is deprotonated, and the resulting enolate is trapped with an appropriate disulfide (symmetrical or mixed) to give sulfide p1 (P is a suitable protecting group for oxygen). The oxygen-protecting group is then removed to give alcohol p2. This intermediate is oxidized via the method of Swern (or using other suitable oxidation conditions), and the resulting aldehyde (not shown) is subjected to a reductive amination reaction to give lactam p3. Acid-catalyzed methanolysis of p3 then affords alcohol p4. This intermediate is oxidized via the method of Swern (or using other suitable oxidation conditions) to the resulting aldehyde (also not shown), which is subsequently subjected to an olefin-forming reaction to provide intermediate p5. This compound may be utilized in place of intermediate O in the above general synthetic methods; alternatively, the lactam-protecting group may be removed to give intermediate P1. 
To synthesize intermediate P2, intermediate C1 is deprotonated, and the resulting enolate is trapped with an appropriate source of electrophilic oxygen (e.g., an oxaziridine) to give alcohol p6. This intermediate is alkylated with a suitably functionalized alkyl halide or triflate to give ether p7 (P is an appropriate protecting group for nitrogen). The nitrogen-protecting group is then removed, and the resulting amine (not shown) is subjected to cyclization conditions to give lactam p8. Acid-catalyzed methanolysis of p8 then affords alcohol p9. This intermediate is oxidized via the method of Swern (or using other suitable oxidation conditions) to the resulting aldehyde (also not shown), which is subsequently subjected to an olefin-forming reaction to provide intermediate P2. 
A synthesis of specific intermediate P3 is now described. Intermediate D1 (described above) is ozonized, and the resulting aldehyde (not shown) is reduced to the corresponding alcohol (also not shown). This intermediate is then protected to afford compound p10 (P1 is an appropriate protecting group for oxygen). The imide functionality present on p10 is hydrolyzed to carboxylic acid p11, and this intermediate is coupled with a suitably protected hydroxylamine derivative to give amide p12 (P2 is an appropriate protecting group for oxygen that is stable to conditions which will remove P1). The P1 protecting group is then removed, and the resulting alcohol (p13) is transformed into an appropriate leaving group (halide or triflate, not shown). The P2 protecting group is then removed, and the resulting hydroxamic acid is cyclized to give intermediate p14. Acid-catalyzed methanolysis of p14 then affords alcohol p15. This intermediate is oxidized via the method of Swern (or using other suitable oxidation conditions) to the resulting aldehyde (not shown), which is subsequently subjected to an olefin-forming reaction to provide intermediate P3. 
Specific Method III describes the preparation of intermediates Q1, Q2, and Q3, which may be utilized in the general methods described above. The known compound I1 is transformed into the literature molecule J1 by a modification of a published procedure (Ikuta et al., J. Med. Chem. 1987, vol. 30, p. 1995). Independently, the amino acid ester K1 is protected to afford silyl ether L1. The ether is reduced with DIBAL (or using other suitable reduction conditions), and the resulting aldehyde (not shown) is subjected to an olefin-forming reaction with intermediate J1, producing M1. Silyl deprotection of M1 then affords alcohol N1. This intermediate is subjected to a variety of hydrogenation conditions to provide intermediates Q1, Q2, and Q3. These intermediates may be transformed into intermediates analogous to intermediate O1 (see Specific Method I above) by oxidation and subsequent olefination. 
The artisan will recognize that various compounds of the invention may be made by following the above-described general and specific methods as well as teachings in the art, including the references cited herein, the disclosures of which are hereby incorporated by reference. Additionally, the artisan may prepare various compounds of the invention according to the example described below or through routine modifications to the syntheses described herein.